You should check out this Mind Field episode. It's harsher than it looks, but for that amount of money I'd attempt it anyway.
I think I would end up playing with my food a lot to pass the time. Like that game where you get a bottle of water to stand on end, or making sculptures out of mash potatoes, that sort of thing. If I get bored with that I'd resort of mental mathematics. I'd also try to keep physical active, push-ups, sit-ups, etc.